There are lots of threads on this if you wish to do a search but both of your complaints sound like a settings issues. If your footage is exposed OK but you don't like the colors or contrast, that is a setting issue and can be fixed in-drone or with post processing.
Careful with polarizers because you cannot just leave them on or "set and forget". The way polarizers work, the effect is strongest 90 degrees to the sun and eliminated 180 degrees to the sun. Any movement you make with the drone in flight that changes the angle to the sun will change the look of your footage, and most people do not want uneven footage.
I don't know what shooting conditions you most often shoot in, but a good place to start would be with ND8/ND16/ND32 or something close to that depending on conditions. Also if they aren't polarized, you have much more freedom while flying without ruining the footage.
Also do yourself a favor and read up on how video exposures work (shutter speeds, apertures, ISO, etc.) if you have not already.